Stripped-envelope core-collapse supernova $^{56}$Ni masses: Persistently larger values than supernovae type II

Abstract

Context. The mass of synthesised radioactive material is an important power source for all supernova (SN) types. Anderson (2019) recently compiled literature values and obtained 56 Ni distributions for different core-collapse supernovae (CC SNe), showing that the 56 Ni distribution of stripped envelope CC SNe (SE-SNe: types IIb, Ib, and Ic) is highly incompatible with that of hydrogen rich type II SNe (SNe II). This motivates questions on differences in progenitors, explosion mechanisms, and 56 Ni estimation methods. Aims. Here, we re-estimate the nucleosynthetic yields of 56 Ni for a well-observed and well-defined sample of SE-SNe in a uniform manner. This allows us to investigate whether the observed SN II-SE SN 56 Ni separation is due to real differences between these SN types, or because of systematic errors in the estimation methods. Methods. We compiled a sample of well observed SE-SNe and measured 56 Ni masses through three different methods proposed in the literature. First, the classic 'Arnett rule', second the more recent prescription of Khatami & Kasen, and third using the tail luminostiy to provide lower limit 56 Ni masses. These SE-SN distributions were then compared to those compiled by Anderson. Results. Arnett's rule -as previously shown -gives 56 Ni masses for SE-SNe that are considerably higher than SNe II. While for the distributions calculated using both the Khatami & Kasen prescription and Tail 56 Ni masses are offset to lower values than 'Arnett values', their 56 Ni distributions are still statistically higher than that of SNe II. Our results are strongly driven by a lack of SE-SN with low 56 Ni masses (that are in addition strictly lower limits). The lowest SE-SN 56 Ni mass in our sample is of 0.015 M , below which are more than 25% of SNe II. Conclusions. We conclude that there exists real, intrinsic differences in the mass of synthesised radioactive material between SNe II and SE-SNe (types IIb, Ib, and Ic). Any proposed current or future CC SN progenitor scenario and explosion mechanism must be able to explain why and how such differences arise, or outline a yet to be fully explored bias in current SN samples.

Comparing Moment-Based and Monte Carlo Methods of Radiation Transport Modeling for Type II-Plateau Supernova Light Curves

“…The release of the initial thermal radiation leads to a higher bolometric luminosity than the instantaneous nuclear decay luminosity. The slopes of the decay tails are steeper than the analytical prediction that assumes total trapping, consistent with the expectation of gamma-ray leakage from 1 2 3 4 5 6 7 8 9 10 the ejecta (Clocchiatti & Wheeler 1997;Wheeler et al 2015;Meza & Anderson 2020). The steeper slope from the STELLA model is likely due to an underestimation of gamma-ray deposition by the Swartz et al (1995) scheme.…”

The Nickel Mass Distribution of Stripped-Envelope Supernovae: Implications for Additional Power Sources

“…Indeed, the accuracy of the M Ni estimates for SESNe has been disputed in recent years (Dessart et al 2016;Sukhbold et al 2016;Khatami & Kasen 2019;Meza & Anderson 2020). Unlike H-rich SNe for which M Ni is estimated by model-2 Although these results should be interpreted with caution since ejecta masses are often obtained from Arnett-like models, for which some assumptions break down in the case of SESNe as discussed in this paper.…”

“…Further studies of stellar populations in the vicinity of SESNe sites indicate that Type IIb, Ib, and Ic SNe are progressively found in younger stellar populations, suggesting that they arise from more massive progenitors (Maund 2018). In addition, a key piece of evidence that has been particularly problematic for the binary scenario is the reported 56 Ni masses of SESNe, which are systematically larger than those of Hrich Type II SNe (Anderson 2019;Meza & Anderson 2020). This may suggest that the progenitors of SESNe are initially more massive that those of H-rich Type II SNe, which is more naturally predicted by the evolution of single stars.…”

Understanding the extreme luminosity of DES14X2fna

“…Again, this is not a Gaussian uncertainty, instead reflecting the maximum possible deviation due to uncertainty in explosion epoch. Meza & Anderson (2020) finds SNe IIb and Ib 56 Ni masses which typically vary from ∼ 0.03 − 0.2 and ∼ 0.02 − 0.13 M using these methods respectively. DES14X2fna would require a 56 Ni mass that is ∼ 4-5 times larger than is typical for SNe IIb.…”

“…Some other types of core-collapse SNe are primarily driven by different physical processes (e.g. interaction with a surrounding circumstellar material (CSM) for SNe IIn; Moriya et al 2013), although a 56 Ni decay model can still be used to estimate some explosion properties (e.g., Prentice et al 2016;Meza & Anderson 2020). For SNe with light curves driven by 56 Ni decay such as SNe IIb, a more luminous SN indicates a higher synthesised mass of 56 Ni to power the peak of the light curve.…”